Mayo v. Prometheus – U.S. Supreme Court raises further questions

Posted By Rachel Tonelli-Zasarsky – Apr. 20, 2012

On March 20th, 2012, Justice Breyer, speaking for the Supreme Court of the United Sttes in the case of Mayo v. Prometheus, held that Promethus’ patent claims in No. 6,355,623 and No. 6,680,302 were invalid because the claims effectively embodied laws of nature.

The definition of patentable subject matter in the United States is found in Section 101 of the Patent Act:

“Whoever invents or discovers any new and useful process,machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent thereof, subject to the conditions and requirements of this title”

However, precedent dictates that “laws of nature, natural phenomena, and abstract ideas” constitute an exception to s. 101 and are therefore not patentabe” (Diamond v. Diher).

At issue in this case were process claims such as Claim 1 of No. 6,355,623 which states that:

“A method of optimizing therapeutic efficacy for treatment of an immune-mediated gastrointestinal disorder, comprising:“(a) administering a drug providing 6-thioguanine to a subject having said immune-mediated gastrointestinal disorder; and “(b) determining the level of 6-thioguanine in said subject having said immune-mediated gastrointestinal disorder, “wherein the level of 6-thioguanine less than about 230 pmol per 8×108 red blood cells indicates a need to increase the amount of said drug subsequently administered to said subject and“wherein the level of 6-thioguanine greater than about 400 pmol per 8×108 red blood cells indicates a need to decrease the amount of said drug subsequently administered to said subject.”

The court interpreted such claims as a three step process instructing doctors to measure the level of the metabolite (6-thioguanine), use the law of nature to calculate limits, and finally reconsider the dose of drug to be administered. Justice Breyer maintained that “these instructions add nothing to the specific laws of nature”, and therefore the claims are not patentable.

After reading the decision, I could not help but ask the question: “but what about the threshold”. Certainly the laws of nature and the process allow one to determine the level of the metabolite in the blood, but the measurement is meaningless without a comparator. The quoted “230 pmol per 8×108 red blood cells” and “400 pmol per 8×108 red blood cells” represent the triggers for decision making. These numbers are limits, comparators, and not laws of nature in and of themselves. They are a diagnostic tool which can be used only once a measurement through a law of nature is made, yes, but that measurement is not what the patent seeks to protect. The patent seeks to protect the trigger. This trigger is, in my opinion an “improvement” of the process of drug administration in this scenario: it eliminates the trial and error approach, in favour of a methodical one.

In Canada, the fact that laws of nature cannot be patented is embodied in s.27(8) of the Patent Act, whereby “No patent shall be granted for any mere scientific principle or abstract theorem”. Most definitely if a Canadian court had interpreted these patent claims as Justice Breyer did, Prometheus’ patent would have been found to be invalid here too. The question remains then, did Justice Breyer incorrectly fail to account for the “trigger”, by simply sweeping it under the rug as part of a process?